Silver oxide, silver sulfide, and other silver by-products (“silver soils”) build-up, in photofinishing equipment. In modem photofinishing, an automated process uses at least three separate tanks and associated solutions: a developer tank containing the developer solution that reduces the silver in the latent image to metallic silver, a fixer tank containing a fixer solution to remove undeveloped silver halide salts, and a wash tank containing a wash bath to remove residual fixer. These tanks are connected by a mechanized conveyance system, such as rollers, belts, and/or racks, to carry the photographic material between the tanks. After use of such automated processors, silver soils accumulate on the equipment thereby affecting the processor performance.
These silver soil deposits may contain silver, silver salts, silver oxide and silver sulfide. In the past, cerium solutions have been suggested, to clean silver soil U.S. Pat. No. 5,198,141. Various other solutions have also been used including bleach, chromic acid, sulfuric acid, and citric acid. See e.g. U.S. Pat. No. 4,678,597; U.S. Pat. No. 4,640,713. These solutions may require several hours of soaking and manual scrubbing to effectively remove silver soil. As a result, the intricate equipment, such as the conveyance system and trays, is often disassembled and manually or ultrasonically cleaned. Disassembly methods are not only time-consuming and labor-intensive, but they may lead to a host of mechanical problems.
Tarnish removers also remove silver soils in the form of tarnish, which is a film discoloration of a metal surface that is a result of a chemical reaction of oxygen and sulfur from the atmosphere with the metal surface. The prior art silver soil removers, such as those disclosed in U.S. Pat. No. 2,691,593, typically use an abrasive material, a carrier and a surfactant.